Pumps for liquids or fluids, often having non-microscopic solid particles therein, are well known in the art, and commonly use a rotary or centrifugal action to mechanically impel the fluid in the desired direction.
Typically such pumps are vacuum primed and are positioned above the level of the liquid being pumped. In such installations, the pump will not operate properly unless there is a head of fluid from the lower liquid level into the pump itself. That is, if the fluid does not reach into the pump, the pump will merely drive air and will not create a sufficient force to draw the fluid up to the pump for the desired pumping. Therefore, such pumps are primed with fluid to ensure that there is the desired head of fluid extending into the pump so that it may operate as desired. Moreover, it is important that the pump impeller, mechanical seal or packing be completely submerged in order to prevent air from being entrained in the pump and potentially air locking the impeller to prevent pump operation. This has typically been accomplished by providing a separate vacuum pump, connected to the primary pump at its highest point, to ensure that all air is extracted as desired.
Such separate vacuum pumps must, however, typically be connected to the pressure side of the primary pump, with a valve of some type provided in the vacuum line to the separate vacuum pump to prevent pressurized fluid from entering, and potentially damaging, the separate vacuum pump. In pumps with automatic operation, such valves have, for example, been solenoid valves or the like. However, such valves are prone to leaking after frequent operation, in which case the pressurized water will still force its way through the valve and therefore still potentially damage the separate vacuum pump. Further, such valves cannot be opened while the pump is in operation or the water from the primary pump will undesirably be forced into the separate vacuum pump.
The present invention is directed toward overcoming one or more of the problems set forth above.